The present invention relates to a hydraulic system for a mobile vehicle that supports and positions a load relative to a docking structure, and more particularly to hydraulic control circuitry for a patient transport that supports and positions a patient relative to a medical diagnostic apparatus such as a nuclear magnetic resonance machine.
Various types of patient supporting and positioning apparatus are known in the medical industry. For example, apparatus such as patient beds, stretchers, surgical tables and examination tables are commonly employed. Such apparatus usually are constructed with an articulated structure, and may include various drive mechanisms for elevating and tilting either the entire patient or only a specific portion or limb of the patient, such as to provide a backrest or kneelift. The apparatus thus properly positions a patient or a part of the patient's body for treatment and/or examination by a physician or a medical diagnostic apparatus such as an ultra-sound scanner.
One known apparatus used with radiation/oncology treatment linear accelerator machines includes a stationary base located adjacent the radiation ports of the machine, a table that may be raised or lowered with respect to the base, and a cradle slidably mounted for longitudinal movement on the table. A patient to be treated is first transferred from a gurney onto the cradle, and is then lifted to the approximate treatment height by raising the table. The patient and cradle are next slid outwardly from the table so that the body area to be treated is positioned beneath the radiation ports of the machine. The table is then raised or lowered to provide the appropriate height for treatment.
A relatively recent development in medical diagnostic apparatus is the nuclear magnetic resonance machine or NMR machine. An NMR machine employs a large magnet which scans the desired portions of a patient's body to provide images on a screen for diagnostic purposes. A patient must be placed within the interior of an annular magnet in order for scanning to occur. Therefore, a vehicle which transports a patient to the NMR machine must be capable of precisely positioning a patient relative to this annulus.
Various other unique problems are assocated with NMR machines. In operation, an NMR machine will create an extremely strong magnetic field, and thus only non-ferrous equipment may be employed near the machine. Further, any electronic power sources or electronic controls which are employed either with an NMR machine or a patient transport must be remotely located so that the magnetic field does not effect their operation. Thus, known patient handling equipment, which generally employs ferrous materials and electronic power sources and controls for positioning a patient, cannot be used with NMR machines. Additionally, present life support equipment also employs electronic controls and equipment and therefore must also be remotely located from an NMR machine. As a result, the ability to rapidly disengage a critically ill patient from an NMR machine and remove the patient from the scan room must be provided by the patient transport so that the patient may be quickly attached to such life support equipment in an emergency.